On Sunday, June 30, with Britain already under severe pressure from war and the threat of invasion, Lord Beaverbrook sent Winston Churchill a resignation letter. Beaverbrook opened by stressing how dramatically aircraft output had risen during his seven weeks as minister of aircraft production, arguing that he had accomplished his mission. He said his conflicts with the Air Ministry had become so deep that they now interfered with his work, and he concluded that someone more compatible with the Air Ministry should replace him.

Beaverbrook framed the problem as both personal and institutional. He blamed himself for being unsuited to working with Air Ministry officials and asked to be released once he had briefed a successor. Although he declared that his work was finished, John Colville suspected a less noble motive: that Beaverbrook wanted to leave while his reputation was at its highest, before new difficulties could diminish his apparent success.

Churchill replied the next day, July 1, in a noticeably cold tone, addressing him formally as "Dear Minister of Aircraft Production." Churchill made clear that, with invasion said to be imminent, he would not accept any ministerial resignation. Instead, Churchill ordered Beaverbrook to put the matter aside and continue what Churchill called his magnificent work, while promising to study how to reduce the overlap and friction between Beaverbrook's ministry and the Air Ministry.

Beaverbrook answered at once. He said he would not neglect his duties during an invasion crisis, but he repeated that the transfer of the ministry should happen soon because he still could not get the information, supplies, and permissions he believed were necessary to build reserves. He insisted that the breach with reluctant officers could not be healed, yet he stopped short of renewing an immediate threat to resign. Churchill was relieved, because losing Beaverbrook would have created a major gap in both aircraft production leadership and Churchill's personal circle of advisers, and that same night Churchill summoned him to 10 Downing Street for another urgent matter.